Recreational water systems such as swimming pools, spas, hot tubs, and jetted tubs, are commonly treated with chlorinated derivatives of cyanuric acid (1,3,5-triazine-2,4,6(1H,3H,5H)-trione) in order to disinfect the water and maintain sanitary conditions. The action of these chlorinated cyanuric acid derivatives, typically referred to by the trade names di- or trichlor, is attributed to the generation of free chlorine as HOCl and OCl-arising from the hydrolytic equilibria of the various chlorinated species (O'Brien et al., 1974). When used in this way there is a gradual accumulation of residual cyanuric acid in the water (Downes et al., 1984). As the level of cyanuric acid rises, free chlorine's ability to act as a disinfectant is weakened due to increased complexation of chlorine. Above about 50 ppm cyanuric acid, the time it takes to kill bacteria in chlorinated water increases versus similarly treated water without cyanuric acid. In heated systems, such as hot tubs and spas, at even moderate levels of cyanuric acid the amount of time it takes chlorine to kill a common pathogen such as pseudomonas aeruginosa can be as much as one hundred times as long as similar systems without cyanuric acid.
A 2007 study by the United States Centers for Disease Control and Prevention (Shields et al., 2007) revealed that cyanuric acid significantly diminishes chlorine's ability to inactivate chlorine-resistant porotozoan and cryptosporidium. Based on these findings several state and local Departments of Health have issued recommendations to the recreational water industry that cyanuric acid levels not exceed 30 ppm.
It is a common practice in the recreational water industry to reduce excess cyanuric acid levels by partially draining pools, tubs, spas, holding tanks, etc., and refilling with fresh water. This is a labor intensive and costly solution, particularly in areas affected by prolonged drought such as Southern California where the cost to replenish a typical 20,000 gallon swimming pool with fresh water is prohibitively high. Accordingly, a need exists in the recreational water industry for compositions and methods to reduce excess cyanuric acid levels that do not require a draining and replenishing